Wireless devices, such as cellular telephones, are increasingly using location-based services. In a typical example, an application running on a wireless device could obtain an estimated location of the wireless device and then use that estimated location to provide some type of service to the user of the wireless device, such as showing the estimated location on a map, providing directions, or identifying nearby restaurants or other businesses.
The estimated location could be obtained using any number of location-determination techniques. In one possible approach, the wireless device may receive wireless signals from multiple satellite-based transmitters. The Global Positioning System (GPS) is an example of this approach. In another possible approach, the wireless device may receive wireless signals from multiple terrestrial-based transmitters. Advanced forward link trilateration (AFLT) is an example of this approach. In yet another possible approach, the estimated location of the wireless device may be determined based on the cell or the cell-sector that is currently serving the wireless device. For example, a centroid that was previously calculated for the cell-sector may be given as the estimated location of the wireless devices.
The estimated locations that are obtained in such approaches can have differing levels of uncertainty. Thus, an application that obtains an estimated location of a wireless device may also obtain an estimate of the uncertainty associated with the estimated location. In the case of estimated locations that are obtained using wireless signals from satellite-based transmitters or terrestrial-based transmitters, the uncertainty may depend on the characteristics of the wireless signals themselves and/or on the number of transmitters that are used. In the case of an estimated location that is obtained based on the cell-sector that is currently serving the wireless device, the uncertainty is often estimated based on calculated boundaries of the cell-sector.